Vacuum versus Pressure

[Craftdiggity]

I am going to try casting some of this Staghorn Cactus I just got, along with some Jarrah Burl (very porus). I just got my new vacuum chamber from MesquiteMan and I am anxious to use it, but I'm not sure if this is the correct application. Would you go with the vacuum chamber, or cast these under pressure?

 

[Padre]

The rule of thumb I use, that I got from IAP is:
Casting=pressure; stabilization=vacuum

 

[Bellsy]

Chris,

What are you going to use as a casting medium? I can assume that you are going to use Alumilite if you have been dealing with Curtis. If that's the case...it's Pressure.

On the other hand the vacuum chamber you received is for just that...vacuum. The cactus is does not need stabilizing that I know of (correct me if I'm wrong). The stabilizing is done in conjunction with the new "juice" that Curtis is promoting.

Dave

 

[Craftdiggity]

I am using PR. I guess I just don't understand why the vacuum wouldn't work. If the goal is to remove air, wouldn't vacuum do that? Eliminate air bubbles and pockets?

 

[PTownSubbie]

I am using PR. I guess I just don't understand why the vacuum wouldn't work. If the goal is to remove air, wouldn't vacuum do that? Eliminate air bubbles and pockets?

All it really does is allow the bubble to expand. If you have air on the inside, it will reduce the pressure in the chamber which will increase the size of the bubble.

Padre had my thoughts exactly.....
casting=pressure stabilization=vacuum

 

[PenMan1]

With Cactus, IMHO you MUST have one or the other, pressure or vacuum. Since you are using PR, my preference would be pressure. BUT, that is only my opinion. Other PR casters perfer vacuum with pourous materials.

Roy, Oklahoman does MUCH cactus in PR. I would certainly value his opinion, as his cactus pens are beautiful.

Respectfully submitted.

 

[PenMan1]

In the case of cactus, the goal is as much to force as much resin as possible into every tiny void in the cactus. That's why my preference would be pressure over vacuum.

 

[MesquiteMan]

Like Fred said, vacuum is going to cause the air within the blank to expand and "float" to the surface. Any overhang within the material will fill up with air until it spills out but it will still be full of air. If you can pull the vacuum and then release it before the resin sets, then that would work since then you are using the atmospheric pressure (14.7 psi at sea level) to reduce the air pocket. Then again, if you just use pressure, you will reduce it much better.